1. Field of the Invention
The present invention relates to a video signal processor for converting digital RGB data into a composite video signal (NTSC system, for example) through a digital analog converter for delivery to a CRT display unit.
2. Description of the Prior Art
A prior art picture video processor supplies signals for displaying a predetermined picture chromatically, for example, by outputting analog signals providing amplitude values for each color component R (red), G (green) and B (blue) to a special monitor set.
The picture signal processor stores picture data in a video RAM, reads the picture data out of the video RAM for each image, addresses a color data RAM having stored R, G, B color data with the picture data as address signal, and subjects the color data read out of RAM to D/A conversion, thereby generating an analog RGB signal. The analog RGB signal is then output to the monitor set to display a color picture.
When outputting a composite signal according to the NTSC system, an operation is carried out on the R, G, B color data generated from the color data RAM, and a luminance signal and two color-difference signals are derived from the operation result, thus obtaining a composite video signal.
According to another example, digital RGB color data is converted once into analog RGB signals through a D/A converter, and the three signals are subjected to analog addition and subtraction to generate a luminance signal (Y), a red color-difference signal (R-Y) and a blue color-difference signal (B-Y), thus obtaining a composite video signal.
However, since the prior art video signal processors obtain the luminance signal and the color-difference signals by operating on each picture element, or pixel, there remain problems because:
the processor must inevitably be large in size; PA1 power consumption is high; PA1 conversion rate is low; and so forth.
Then, in the case of analog processing, the analog signal must have a very high resolution, and in either the NTSC or PAL system it is difficult to handle a high resolution composite signal.